UNIPROT:P20020 - FACTA Search

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Query: UNIPROT:P20020 (adenosine triphosphatase)
3,299 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A Mg2+- and Ca2+-stimulated adenosine triphosphatase (ATPase) at the outer surface of intact Ehrlich ascites tumor cells is described. A surface-bound adenosine triphosphate (ATP)-splitting activity at a lower rate was also demonstrated in the absence of Ca2+ but with Mg2+, Na+, and K+ present in the isotonic medium. Hence, when part of the Mg2+ was exchanged for Ca2+, a marked increase of the ATP-splitting activity was observed. The stimulatory effect of Ca2+ was seen only if both Na+ and K+ were present in the isotonic incubation medium. Thus, the enzyme activity was Mg2+- and Ca2+-dependent. Ca2+, together with the monovalent cations was inhibitory compared with Mg2+ under similar conditions. The apparent Km for ATP for the Mg2+-stimulated ATPase is 0.05 mM, while that of the Mg2+- and Ca2+-stimulated enzyme is 0.10 mM. The Vmax of the former is 0.8 mu-mole per 100 mg Schneider protein per 30 sec compared with 1.92 mu-moles per 100 mg Schneider protein per 30 sec for the latter. The calculated Km for the Mg2+- and Ca2+-stimulated ATPase after subtraction of the Mg2+-stimulated part is 0.22 mM. Ethacrynic acid and N-ethylmaleimide both inhibited the Mg2+- and Ca2+-stimulated ATPase by about 10 percent, while the ouabain inhibition was 15 percent. Cytochalasin B did not influence the enzyme activity, whereas La3+ had a slight stimulatory effect.
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PMID:A Mg2+- and Ca2+-stimulated adenosine triphosphatase at the outer surface of Ehrlich ascites tumor cells. 12 5

Two types of canine cardiac myosins, from the free wall of the left ventricle and from the free wall of the right ventricle, were compared with canine skeletal muscle myosin from gastrocnemius. For K+ -activated myosin the Vmax values in mumoles of Pi/mg.min were: right ventricle, 0.57 +/- 0.02; left ventricle, 0.72 +/- 0.09; gastrocnemius, 0.92 +/- 0.04. For Ca++ -activated myosin the Vmax values were: right ventricle, 0.32 +/- 0.04; left ventricle, 0.42 +/- 0.03; gastrocnemius, 0.52 +/- 0.02; (p greater than 0.01 for all defferences). For all three types of tissues the Vmax values for NH4+ -activated myosin were the same (2.30 +/- 0.11). Corresponding to kinetic changes there were significant changes in the proportion and type of myosin subunits. In the two cardiac ventricles where heavy chains were immunologically identical, 81% of the total nitrogen of right ventricular myosin was present in the heavy chains whereas in left ventricular myosin 90% of the total nitrogen of myosin was present in the heavy chains. Quantifications were made on polyacrylamide gels were dye binding was directly related to nitrogen concentration for each of the myosin chains. In canine skeletal muscle gastrocnemius where the myosin heavy chains were immunologically nonidentical with those of cardiac myosin, 87% of the total nitrogen was present in the heavy chains. The data suggest that there are 2 moles of myosin light chains per mole of myosin heavy chains in right ventricular myosin where the adenosine triphosphatase (ATPase) activity is low and 1 mole of myosin light chains per mole of myosin heavy chains in left ventricula myosin where ATPase activity is elevated; for skeletal muscle myosin there were 1.5 moles of myosin light chains per mole of myosin heavy chains. Proportion of myosin light chain C1 to light chain C2 was the same in both left and right ventricular myosin. In skeletal muscle myosin the proportion of light chain C1 to light chain C2 was significantly different from that of cardiac tissue. It appears that the proportion of myosin light chain C1 to light chain C2 is directly related to the type of myosin heavy chain present since the immunologically identical heavy chains of cardiac tissue were immunologically nonidentical with those of skeletal muscle myosin.
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PMID:Comparative analyses of skeletal and cardiac myosins. 12 33

The ATP-energy transducing system in membranes of Escherichia coli is inhibited by dicyclohexylcarbodiimide. The protein component of this complex with which carbodiimides covalently react to inhibit function was previously identified by labeling wild type and dicyclohexylcarbodiimide-resistant mutants with dicyclohexyl[14C]carbodiimide (Fillingame, R. H. (1975) J. Bacteriol. 124, 870-883). This specific carbodiimide-reactive protein has now been purified. The protein was extracted from the membrane with chloroform:methanol and chromatographed on DEAE-cellulose and hydroxypropyl Spehadex G-50 in this sulvent mixture. The resultant 700-fold purification yielded a protein that was homogeneous on dodecyl sulfate-acrylamide gel electrophoresis and virtually free of phospholipid. It remained soluble in neutral chloroform:methanol throughout the purification procedure. The amino acid composition of the purified protein was extraordinary in that only 16% of the amino acids present could be considered polar. Histidine, serine, cysteine, and tryptophan were not found. Abnormally high contents of methionine, glycine, alanine, and leucine were present. One mole of lysine and threonine were found/mole of dicyclohexyl[14C]carbodiimide bound. The minimum molecular weight based on the amino acid composition was 8400. The specific carbodiimide-reactive protein has also been purified without prior modification by dicyclohexylcarbodiimide. The unmodified protein eluted from DEAE-cellulose at a higher salt concentration than the dicyclohexylcarbodiimide-modified form, which suggested that the reaction with the carbodiimide neutralized the negative charge. Only one-third of the total carbodiimide-reactive protein in the membrane was modified by dicyclohexylcarbodiimide under conditions which maximally inhibited adenosine triphosphatase activity. These results rais the possibility that the carbodiimide-reactive protein may be present as an oligomer in the energy-transducing complex. The purification of the unmodified carbodiimide-reactive protein should permit assessment of tis biological function, particularly its role in the protein-translocation process that is catalyzed by this energy-transducing complex.
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PMID:Purification of the carbodiimide-reactive protein component of the ATP energy-transducing system of Escherichia coli. 78 71

The relationship between the (Na(+) and K(+))-activated adenosine triphosphatase enzyme system implicated in sodium-transport by cell membranes and the calcium-activated adenosine triphosphatase, which is generally associated with calcium uptake, was examined in microsomes from skeletal muscle. Whereas sodium and potassium did not modify the relatively low adenosine triphosphatase activity seen in the absence of calcium, a pattern similar to that of the sodium-transport enzyme system was seen afer the addition of CaCl(2). The calcium-activated adenosine triphosphatase was stimulated equally by sodium or potassium alone, but both the rate and extent of calcium uptake were enhanced more by potassium than by sodium at concentrations below 0.12 mole per liter. In the absence of either of these ions addition of calcium failed to activate adenosine triphosphatase although significant amounts of calcium were taken up by the microsomes.
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PMID:Sodium and potassium effects on skeletal muscle microsomal adenosine triphosphatase and calcium uptake. 422 41

The preparation of cytoplasmic membranes from suspensions of Staphylococcus aureus lysed by an enzyme recently isolated in these laboratories is described. These membranes contained: protein, 34.4%; ribonucleic acid, 6.6%; lipids, 34.5%; and total phosphorus, 1.4%. Such membranes exhibited adenosine 5'-triphosphatase (E.C. 3.6.1.3) activity, liberating orthophosphate at an initial rate of 0.53 mumole per min per mg of protein under optimal conditions. The enzyme was Mg(++)-dependent and K(+)- or Na(+)-stimulated. Maximal activity was observed with a molar adenosine 5'-triphosphate (ATP) to Mg(++) ratio of 1. One mole of orthophosphate was liberated per mole of ATP; the other product of digestion was adenosine 5'-diphosphate. Inorganic pyrophosphate and the 5'-triphosphates of guanosine, uridine, and cytidine were also attacked by membrane preparations, but more slowly than ATP. Ouabain, p-chloromercuribenzoate, and 2,4-dinitrophenol did not alter adenosine triphosphatase activity, whereas both Atebrine and chlorpromazine were inhibitory.
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PMID:Adenosine triphosphatase in isolated membranes of Staphylococcus aureus. 423 Aug 57

1. The rates of translocation of oxaloacetate and l-malate into rat liver mitochondria were measured by a direct spectrophotometric assay. 2. Penetration obeyed Michaelis-Menten kinetics, and apparent K(m) values were 40mum for oxaloacetate and 0.13mm for l-malate. 3. Arrhenius plots of the temperature-dependence of rates of penetration gave activation energies of +10kcal./mole for oxaloacetate and +8kcal./mole for l-malate. 4. The translocation of both oxaloacetate and l-malate was competitively inhibited by d-malate, succinate, malonate, meso-tartrate, maleate and citraconate. The K(i) values of these inhibitors were similar for the penetration of both oxaloacetate and l-malate. 5. Rates of penetration were stimulated by NNN'N'-tetramethyl-p-phenylenediamine dihydrochloride plus ascorbate under aerobic conditions or by ATP under anaerobic conditions. 6. The energy-dependent stimulation of translocation was abolished by uncouplers of oxidative phosphorylation. Oligomycin A, aurovertin, octyl-guanidine and atractyloside prevented the stimulation by ATP, but did not inhibit the stimulation by NNN'N'-tetramethyl-p-phenylenediamine dihydrochloride plus ascorbate. 7. Mitochondria prepared in the presence of ethylene-dioxybis(ethyleneamino)tetra-acetic acid did not exhibit the energy-dependent translocation, but this could be restored by the addition of 50mum-calcium chloride. 8. Valinomycin or gramicidin plus potassium chloride enhanced the energy-dependent translocation of oxaloacetate and l-malate. 9. Addition of oxaloacetate stimulated the adenosine triphosphatase activity of the mitochondria, and the ratio of ;extra' oxaloacetate translocation to ;extra' adenosine triphosphatase activity was 1.6:1. 10. Possible mechanisms for the energy-dependent entry of oxaloacetate and l-malate into mitochondria are discussed in relation to the above results.
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PMID:Factors affecting the translocation of oxaloacetate and L-malate into rat liver mitochondria. 423 43

1. A study has been made of the cellular content and movement of Ca across the membrane of human red blood cells.2. The [Ca] in the cellular contents of fresh red cells is 4.09 x 10(-2) mM. The intracellular concentration of free ionic Ca ([Ca(2+)]) is considered to be less than this value and therefore less than extracellular [Ca(2+)] under normal conditions.3. Observation of unidirectional Ca fluxes with (45)Ca confirms previous reports of low permeability of the red cell membrane for Ca. After nearly 1 week of loading in the cold, intracellular (45)Ca content is 1.8% of extracellular (45)Ca content. Appearance in extracellular fluid of (45)Ca from coldloaded cells can be considered to arise from two compartments. Efflux of (45)Ca from the ;slower compartment' is accelerated by the addition of glucose.4. Starved red cells, incubated at 37 degrees C, after reversible haemolysis for loading with Ca and Mg-ATP, exhibit an outward net transport of Ca against an electrochemical gradient. The transport is associated with the appearance of inorganic phosphate (P(i)). Cells treated similarly, but without ATP show no transport and no appearance of P(i).5. During the initial phase of transport, 1.3 mole P(i) appear per mole Ca transported.6. The transport of Ca from ATP-loaded cells is highly temperature-dependent, with a Q(10) of 3.5.7. Cell membrane adenosine triphosphatase (ATPase) activity of reversibly haemolysed cells is stimulated only by intracellular, and not by extracellular Ca.8. Neither Ca transport in reversibly haemolysed cells, nor the Ca-Mg activated ATPase of isolated cell membranes is sensitive to Na, K, ouabain or oligomycin.9. Mg is not transported under the conditions which reveal Ca transport, but Mg appears to be necessary for Ca transport.10. Sr is transported from reversibly haemolysed Mg-ATP-loaded cells. Sr also can substitute for Ca, but not for Mg, in the activation of membrane ATPase.11. It is concluded that, in addition to a low passive permeability, an active extrusion mechanism for Ca exists in the human red cell membrane. This extrusion mechanism, in addition to a low passive membrane permeability for Ca, may represent the means by which intracellular Ca content is maintained at a low level. It is suggested that the Ca-Mg activated membrane ATPase and the active transport of Ca are two manifestations of the same process.
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PMID:Calcium movements across the membrane of human red cells. 423 81

Plasma membranes were isolated from the ameba Acanthamoeba castellanii by low-speed velocity centrifugation followed by equilibrium centrifugation in a sucrose gradient. The isolated membranes had a high ratio of sterol to phospholipid (0.98 moles/mole) and of phospholipid to protein (0.43 mg/mg). The plasma membranes had very low concentrations of DNA, RNA, lipid inositol, and glycerides. Glycolipids and glycoproteins were enriched in the plasma membranes relative to their concentrations in the whole cell. The plasma membranes were also judged to be of high purity by the absence, or very low level, of enzymatic activities considered to be indicative of other cell membranes, and by electron microscope examination. Alkaline phosphatase and 5'-nucleotidase activities were enriched in the plasma membranes 13-fold relative to the whole homogenate and had higher specific activities in the plasma membranes than in any other cell fractions. A Mg(++) adenosine triphosphatase (ATPase) was enriched sixfold in the plasma membranes relative to the whole homogenate. The phospholipids of the plasma membranes contained more phosphatidylethanolamine and phosphatidylserine and less phosphatidylcholine than did the phospholipids of the whole cells. There were differences in the fatty acid compositions of corresponding phospholipids in the plasma membranes and whole cells but no difference in the ratios of total saturated to unsaturated fatty acids. The membranes of phagosomes isolated from amebae that had ingested polystyrene latex had essentially the same phospholipid, sterol, and enzymatic composition as plasma membranes.
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PMID:Plasma and phagosome membranes of Acanthamoeba castellanii. 432 20

Abnormalities in calcium flux have been linked to abnormal contractile behavior of the heart in patients with congestive heart failure as well as in animal models. Decreased activity or levels of the calcium adenosine triphosphatase of the sarco(endo)plasmic reticulum (SERCA2) particularly have been known to cause a delay in calcium transients. The SERCA2 protein pumps 2 moles of calcium per mole of adenosine triphosphate (ATP) split from the cytoplasm into the sarcoplasmic reticulum, thus lowering the free cytoplasmic calcium concentration. It therefore is of interest to identify mechanisms by which SERCA activity could be increased in the heart. To determine influences of increased expression of the SERCA2 gene on calcium transient and contractile behavior, we constructed transgenic mice and rats expressing a SERCA2 transgene in their heart. In these animals, a 20% increase in SERCA levels occurs due to additional expression of the SERCA transgene. This leads to a corresponding increase in contractile activity as determined by the increase in left ventricular pressure measured as dP/dt(max) and decrease in diastolic ventricular pressure determined as dP/dt(min). Similarly, isolated cardiac myocytes obtained from the heart of transgenic mice showed an accelerated calcium transient and increased speed of shortening and relengthening as determined by edge detection. To determine if SERCA2 transgene expression could have a compensatory effect on the contractile behavior of the heart in transgenic mice expressing SERCA2, these mice were made hypothyroid, and papillary muscle function was determined. Contractile behavior of the papillary muscle of wild-type hypothyroid mice showed a significant increase in muscle relaxation time (RT50). In contrast, SERCA2 transgenic hypothyroid mice showed normal contractile behavior of papillary muscle. A compensatory effect of SERCA transgene expression was therefore demonstrated. In addition, we constructed transgenic rats expressing a SERCA2 transgene in which constriction of the ascending aorta induced cardiac hypertrophy and a delayed contraction of papillary muscle. In preliminary results, we found that SERCA2 transgenic rats submitted to ascending aortic constriction did not show the delayed relaxation of papillary muscle as was found in wild-type rats submitted to aortic constriction. In addition, adenoviral vectors expressing transgenes for calcium-handling proteins can be used to improve cardiac myocyte contraction. Adenoviruses expressing a SERCA transgene or a mutant phospholamban transgene exhibiting dominant negative action were used to infect isolated myocytes treated with a phorbol ester (phorbol 12-myristate 13-acetate), which delays the calcium transients. The calcium transients and contractile behavior of the isolated myocytes indicated that increased SERCA expression or increased expression of mutant phospholamban transgene led to increased SERCA2 activity, resulting in an increased contractile phenotype. Recent findings by other investigators also indicate that decreased SERCA2 activity can be increased under in vivo conditions using adenoviral vector-based SERCA2 expression. A gene therapy type of approach delivering increased amounts of SERCA or phospholamban mutants leading to increased SERCA activity should therefore be considered in the future.
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PMID:Calcium regulatory proteins and their alteration by transgenic approaches. 1075 May 95

The presence of specific adenosine triphosphatase (ATPase) is demonstrated in the eccrine sweat gland units in the scalp of the rhesus monkey (0.2 moles/kg dry wt/hr) and in the sole of the pigtail macaque (1 mole/kg dry wt/hr). This ATPase is activated by combination of Na+ and K+, and this activation is counteracted by ouabain (10(-5) M) which is a specific inhibitor of Na+ transport. Thus, the occurrence of Na-K-ATPase in the sweat gland unit provides an enzymatic basis for participation of active transport of Na+ in the tissue.
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PMID:Enzymatic basis for active transport of Na+ in the sweat gland unit. 2562 67

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